This application claims the priority benefit of Taiwan application serial no. 87112300, filed Jul. 28, 1998, the full disclosure of which is incorporated herein by reference.
1. Field of the Invention
This invention relates to ink-jet printer technology, and more particularly, to a monolithic ink-jet print head and a method of fabricating the same.
2. Description of Related Art
Ink-jet printers, due to low prices and high-quality print outputs, are very popular in the printer market. An ink-jet printer uses a print head that includes an ink transducer, such as a heater, to heat liquid ink into droplets and then spray the droplets onto paper. One popular type of ink-jet print head is the so-called top shooter, which includes a nozzle device mounted on a print-control chip.
Patents related to the ink-jet printer technology include, for example, the U.S. Pat. No. 4,913,405, which utilizes a laser cutting method to make a nozzle device for ink-jet print head; and the U.S. Pat. No. 4,791,436, which utilizes an electroforming method to make a nozzle device for ink-jet print head.
FIG. 1 is a schematic sectional diagram showing the structure of a conventional ink-jet print head. As shown, this ink-jet print head is composed of two main parts: a print-control chip 10 and a nozzle device 16. The print-control chip 10 includes an array of transducers 12 and a plurality of barrier layers 14 for separating the transducer means 12 from each other. Each of the transducers 12 can be a heater or a piezoelectric device, which is used to heat liquid ink into droplets for spraying onto the paper. The nozzle device 16 is a perforated plate including an array of nozzles 18. By the conventional method, the nozzle device 16 is a separate component that is fabricated separately aside the print-control chip 10. In assembly, the nozzle device 16 is then mounted on the print-control chip 10 by first aligning the nozzles 18 in the nozzle device 16 with the corresponding transducers 12 on the print-control chip 10, and then pressing the nozzle device 16 (while heating the barrier layers 14) against the barrier layers 14 by a pressing force indicated by the arrow 22 so as to attach the nozzle device 16 in the direction indicated by the arrows 20 onto the barrier layers 14. When mounted in position, the nozzles 18 in the nozzle device 16 should be accurately aligned with the corresponding transducers 12 on the print-control chip 10.
In the foregoing ink-jet print head, the nozzle device 16 can be formed either through the laser cutting method of U.S. Pat. No. 4,913,405 or through the electroforming method of U.S. Pat. No. 4,791,436. One drawback to the use of these two methods, however, is that the fabricated nozzle devices would be low in good yield rate since these methods can easily cause the fabricated nozzle devices to be subjected to high stress during fabrication that would then cause formational distortions to the fabricated nozzle devices.
Another drawback is that, during the attachment of the nozzle device 16 to the barrier layers 14, the pressure should be carefully controlled. Otherwise, if overly pressurized, the barrier layers 14 can be distorted in shape that would make them unable to bond the nozzle device 16 securely; and if insufficiently pressurized, the attached barrier layers 14 would easily break apart from the barrier layers 14.
Still another drawback is that, after a long period of use, the nozzle device 16 can nonetheless easily break apart from the print-control chip 10 due to the reason that the nozzle device 16 is typically made of metal, which is significantly higher in thermal expansion coefficient than the barrier layers 14. During the operation of the ink-jet print head, both the nozzle device 16 and the barrier layers 14 will be subjected to heat; therefore, after long period of use, the bonding between the nozzle device 16 and the barrier layers 14 can easily break loose.
From the foregoing description, it can be learned that the conventional method for fabricating an ink-jet print head is difficult and thus costly to carry out, which makes the fabricated ink-jet print head less competitive on the market. Moreover, the utilization of the ink-jet print head is also cost-ineffective since the nozzle device would be individually mounted on the barrier layers.
It is therefore an objective of the present invention to provide a monolithic ink-jet print head and a method of fabricating the same, which can integrate the nozzle device with the print-control chip so that the overall manufacturing cost of the ink-jet print head can be reduced as compared to the prior art.
It is another objective of the present invention to provide a monolithic ink-jet print head and a method of fabricating the same, which can allow the nozzle device to be highly affixed to the print-control chip without having the possibility of detaching from the print-control chip due to poorly controlled pressing.
It is still another objective of the present invention to provide a monolithic ink-jet print head and a method of fabricating the same, which can allow the nozzle device to be reliably affixed to the print-control chip without having the possibility of detaching from the print-control chip due to the nozzle device being significantly higher in thermal expansion coefficient than the barrier layers.
It is still another objective of the present invention to provide a monolithic ink-jet print head and a method of fabricating the same, which can allow the nozzle device to be reliably affixed to the print-control chip without having an adhesive material.
In accordance with the foregoing and other objectives of the present invention, an ink-jet print head and a method of fabricating the same are provided.
The monolithic ink-jet print head is constructed on a print-control chip formed with an array of transducers. An ink barrier layer is then formed from a first polymer over the print-control chip for separating the transducers from each other; and subsequently, a nozzle device is formed from a second polymer over the ink barrier layer.
The second polymer is substantially equal or at least close in thermal expansion coefficient to the first polymer used to form the ink barrier layer. Therefore, the nozzle device would hardly break apart from the ink barrier layer after a long period of use that would easily occur in the prior art due to repeated unequal thermal expansions during operation. Moreover, the monolithic process to fabricate the ink-jet print head also allows the manufacture of the ink-jet print head to be easily carried out for mass production with reduced manufacturing cost through conventional semiconductor fabrication processes.